逆变侧交流电压畸变下HVDC运行特性分析

摘要

The PLL(Phase Locked Loop) output performance and the valve commutation characteristics under the AC-bus voltage distortion of inverter side are deduced to reveal the mechanism of influence brought by the harmonic voltage on the inverter-side CEA (Constant Extinction Angle) controller and VDCOL (Voltage-Dependent Current Order Limiter) and to explain why the harmonic voltage may reduce the reference of inverter-side triggering angel and the transmission capacity of DC system.As the CEA control cannot properly follow its setting under the AC-bus voltage distortion,the gain of current deviation control is reduced to effectively decrease the steady-state error of CEA control and the loss of transfer capacity under the AC-bus voltage distortion.A method for calculating the steady-state operating point of DC system is proposed.PSCAD/EMTDC simulation verifies the correctness of theoretical analysis,the effectiveness of the improved method and the accuracy of calculation method.%推导了逆变侧交流母线电压存在畸变时锁相环的输出特性和阀换相特性,揭示了谐波电压对逆变侧定熄弧角控制器和低压限电流控制器(VDCOL)带来影响的机理,解释了谐波电压的存在会减小逆变侧延迟触发角的指令值、降低直流系统传输容量的原因.针对交流母线电压谐波畸变情况下定熄弧角控制不能很好跟踪其整定值的问题,通过减小电流偏差控制的增益,有效减小定熄弧角控制在交流电压畸变时的稳态误差量,降低了传递容量的损失.提出了谐波影响下直流系统稳态工作点的计算方法.PSCAD/EMTDC仿真验证了理论分析的正确性、改进措施的有效性和计算方法的准确性.